The OP asked a simple question, knows what he wants, and it is a totally reasonable (and inexpensive) way to get more braking power. For a guy his size on a mountain bike, a 203mm front rotor is absolutely appropriate.

Just check that the fork is OK to take a 203mm rotor. I would guess it probably can, but do check. If so, get the larger rotor, two adaptors, and go for it. It will make a noticeable difference.

I would also be sure to get compression-less brake housing.

All of these other solutions (different pads, different brand rotors, cable housing) are fine ways to improve brake performance, but none make the sort of difference that a bigger rotor does. Bigger rotors are not always better if you don’t actually need the power as they can be a bit harder to modulate at lower braking forces. But at the OPs weight, he is using a LOT of braking force.